This invention relates to a safety valve which is designed to eliminate the risk of excessively hot water or steam escaping from a hot water tap or other hot water outlet.
Although at the present time hot water cylinders must be fitted with some form of relief valve or open elevated vent which is designed to relieve or limit excessive pressure in the hot water cylinder, there have been instances where these valves have failed or the vents become blocked causing an explosion, and in some cases death. In other cases because of poor maintenance or poor design, there is insufficient protection against scalding by excessively hot water or steam emerging from a hot water outlet such as a tap or shower rose.
Devices have been used which admit cold water to the hot water line running from a hot water cylinder via a thermostatically-controlled valve to prevent excessive temperatures within the hot water line, but these will be useless if there is no cold water supply e.g. because of frozen pipes. These are also prone to becoming silted-up and to calcium deposits. Electrolytic corrosion can also be a problem.
Where polybutylene hose or pipe is used in a hot water plumbing system this is also particularly susceptible to damage of over-heated. While the pipe itself will withstand temperatures up to 95.degree. C. it is found that, in practice, if a hot water system is heated above 80.degree. C. the pipe can thin beneath the metal clamping rings which are usually used to fasten the pipe to fittings such as T-joints, elbows etc. The pipe does not regain its former thickness on cooling, thus resulting in loose fittings and consequent leakage.
The present invention was therefore devised with the objective of overcoming the above-mentioned disadvantages.